The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Typical automatic and dual clutch transmissions employ a hydraulic control system operable to perform various functions such as controlling various components within the transmission. Examples of these functions include controlling torque transmitting devices, cooling, lubrication, and the actuation of valve assemblies and components. The hydraulic control system typically includes a valve body having a plurality of valves located therein. These valves are connected via a plurality of fluid passages formed within the valve body and within various components of the transmission, such as shafts.
A pressurized hydraulic fluid is communicated through these fluid passages to the various valves within the control system. The valves are then selectively actuated to control the flow of the pressurized hydraulic fluid through the transmission. One type of valve found in dual clutch transmissions having synchronizer assemblies includes a shift actuator valve operable to mechanically move a shift fork in the synchronizer assembly in order to position a synchronizer between a neutral, or unengaged position, and at least one engaged position. In the neutral position, the synchronizer is not engaged with a gear. In the engaged position, the synchronizer is engaged with a gear. It is important that these shift valves have features that prevent unwanted engagement or disengagement of the synchronizer. One example of a feature that assures the shift valve is in the desired position is the use of one or more pressure or flow control solenoids and position sensors that provide feedback to control the actuator position.
While these shift valves are useful for their intended purpose, there is a constant desire to reduce the complexity of the control algorithm which returns the pistons or valves back to a neutral location, while maintaining robust and reliable operation. Accordingly, there is a need in the art for a shift valve assembly that achieves this goal while maintaining sealing and functionality within the control system and providing a tolerance in the range of pressures that actuate the shift valve, resulting in a simple and reliable control valve.